Certificate of Rent Paid

If you want to make a purchase and then be done - buy a Certificate of Deposit. 

You should be able to check on permits pulled related to the ADU and if it has a certificate of occupancy separate from the main house.

The can have their agent send you a Certificate of Insurance.  

As per my understanding there are no CO ( certification of Occupancy) required in Carlisle.

Execution of the plan will start slow, but constant growth will build a financial fortress over time, especially if you learn to diversify in different markets, different housing types, and with all the different vehicles (rentals, syndicates, notes, tax-lien certificates, money lending, options, owner financing, etc.) available to RE Investors.

Such as you will need to use a bank in PR to get a loan, commercial certificates, municipality certificates, etc... these are all the things you should know ahead of time, because they all cost money.The government of PR always has a palm out for money, so just know what you are getting into before you buy. 

(when the house has been vacant for an extended period of time, or a neighbor reports it, Baltimore City can mark it as a vacant  This means you'll also need to get a Certificate of Occupancy [CO] inspection, in addition to any other Baltimore rental, S8, and permitting inspections).None of this was a issue for me because I bought it without any contingencies.   

Just in case, I've already invited him into the property and run my full renovation plan by him, just so we have no surprised when I apply for my Certificate of Occupancy.

I always thought that was an option if the owner wanted to bring the house out of the flood zone by getting some sort of elevation certification saying the house itself is above the 100 year flood plane and therefore does not need flood insurance.